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Morphological, ultrastructural, and transcriptomic characterization of the newly discovered protist lineage SUM-K
Valt, Marek ; Čepička, Ivan (advisor) ; Oborník, Miroslav (referee)
Here I am presenting a novel deep-branching organism, flagellate SUM-K. SUM-K is morphologically inconspicuous protists that occurs in two distinctive forms, immotile "sun- like" form and motile, flagellated form. Sun-like cells are rounded approximately 5 µm big cells that produce numerous thin radial projections artificially resembling Heliozoeans. Based on ultrastructure analysis and light microscopy observations we classified these projections as novel type of extrusomes with putative function of prey predation. Flagellate state moves with one anterior, posterolaterally directed flagellum. The posterior end of the cell bears a long extrusion that resembles a flagellum but is not motile. Based on these morphological characteristics organism can't be classified into any of the establish eukaryotic supergroups. Likewise, phylogenetic analysis based on SSU rDNA failed to resolve its evolutionary position, placing it to relation with Ancoracysta twista, an orphan lineage similarly unclassifiable to any of current eukaryotic supergroups. Robust analysis based on 206 orthologous genes placed SUM-K to relation with Hemimastigophora. Even though the morphology of currently described Hemimastigophoreans and organism SUM-K is incongruent, its relation presents interesting prospective of evolution of...
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